Electrical system grounds provide a circuit with a complete path to enable the flow of current. However, since separate electrical systems typically have different grounding schemes, connecting the separate systems together can cause ground loop problems in which an electrical potential develops between the systems. This potential between the grounds causes unwanted current flow that can degrade data signals, produce excessive electromagnetic interference, and damage components.
An example of such a problem is a telephone repair worker who plugs diagnostic equipment (e.g., portable computer) into a port to effect repairs to a circuit. The diagnostic equipment has its own ground scheme and the circuit under repair has a separate ground scheme. In such a case, the diagnostic equipment needs to be isolated from the circuit under repair to prevent damage to either the diagnostic equipment or the circuit.
One way to isolate the diagnostic equipment from the circuit is by an optical isolator. The optical isolator transforms an input electrical signal into an optical signal and then back to an electrical signal, thus isolating the input signal ground from the output signal ground. The problem with optical isolators is that they limit the speed of data transfers to lower speed operations such as 9600 bps or 19.2 kbps. This is due to the transition time of an optical isolator being slower than the switching frequency of the interface. In other words, the optical isolator circuit is trying to switch so fast that the output signal does not have adequate time to make full transitions. There is a resulting need in the art for a way to isolate circuit grounds of coupled data ports while improving data transfer rates between circuits.